I am fairly new to STATA and statistics in general - I'm thus very sorry
in case my questions appear pretty basic to most of you.

As part of my project I regress a performance variable (DV) on two
explanatory variables, their interaction and a set of controls (IVs).
Both explanatory variables (the interacted ones) are continuous. To
allow for a better interpretation of the interaction many papers present
simple slope graphs of the interactions (basically high/low combinations
of the two variables) combined with significance tests of the slope of
the one variable at the two levels of the other.

I found "Cohen et al. (2003): Applied Multiple Regression/Correlation
Analysis for the Behavioral Sciences" very helpful since they explain
the math in Chapter 7 "Interactions Among Continuous Variables". So I
think I should be able to do both the plotting and testing by hand.
However, I was wondering if there is a (user written) STATA command
available which could be used to create the plots as well as to do the
significance tests.